In biological samples, target molecules (also called analytes) of interest to be identified and quantified are for example vitamins, hormones, drugs, medication, odorous substances, flavoring substances, pesticides, pollutants or any organic compounds. The molecular weight of such target molecules is in most cases below 1000 Da (Da=Dalton=g/mol). Such target molecules may be contained in biomedicine samples, in body fluids (e.g. blood, blood serum, urine), in food (especially beverages), in drinking water or waste water. All those samples, which preferably are liquid and in general have an aqueous matrix, are referred to as biological samples, which are preferred in the present patent application.
The target molecules often are present only as trace substances in the samples. Therefore a method of accumulation has to be applied first, before the concentrated target molecules can be analyzed by a determination method such as gas chromatography (GC), or liquid chromatography (LC, HPLC), or gas chromatography linked with mass spectrometry (GC-MS), or liquid chromatography linked with mass spectrometry (LC-MS). As a method of accumulation, the extraction of target molecules from biological samples by a sorbent, in particular by a sorptive extraction layer, can be applied. Such sorptive extraction layer materials preferably have no pores, but are polymeric materials with low enough glass transition point (Tg), so that the application temperature is above their glass transition point. Above Tg the polymers are in a gum-like or liquid-like flexible state. In this state analytes can enter such homogeneous, non-porous polymers and dissolve in the bulk of the polymer phase.